Hydrogenation catalyst



2,897,160 Patented July 28, 1959 HYDROGENATION CATALYST.

Harold W; Fleming, Louisville, andiR'onald Reitmeier,

Anchorage, Ky., assignors' to Ghemetron Gm'poration,v

a corporation of- Delaware No Drawing. Application February 10, 1958 Serial-No. 714,052

6 GIaims. (Cl; 252 -455) This invention relates generally to the hydrogenation of unsatinatedhydrocarbons and especially to the selective hydrogenationof acetylenic-hydrocarbons in gas mixtures containing olefins and hydrogen. More particularly, the invention involves an improved cobalt-molybdena catalyst'fdr such reactions.

This application is a continuation-in-part of our copending application Serial Number 494,814, filed March 16, 1955, now abandoned.

Acetylenic hydrocarbons, because of the relative instability of their triple bond, may be hydrogenatedmore readily than hydrocarbons containing double'bonds, and selective hydrogenation ofacetylene in a gas mixturecontaining olefins is possible by utilization of a catalystof appropriate activity to cause the hydrogenation of acetylene to occur at a much greater rate than the hydrogenation of the olefins. Such selective-hydrogenationposes a difficultproblem, however, when only smallamounts of acetylene are present inzthegas-mixture and when-it isnecessary to completely hydrogenate the acetylene without appreciably lowering the olefin-content inorder reproduce a gas mixture-suitablefor use'as a synthetic intermediate. ing essentially of olefins and hydrogen for-the-production of polyethylene in general should not contain more than about 25 parts of acetylene per million parts of the mixture. Mixtures containing; higher acetylene. concentrations' have been found tobe unsuitable for the-polymerization reaction.

An important object'of this invention is to' providea catalyst which is:capableof hydrogenating small'am'ounts of acetylenes. in gas mixtures in such manner: that the reaction proceeds virtually to completion at a highvelocity' to reducethe acetylenes content to a few parts per million, and, since any olefins which. are: hydrogenated in a gas mixture containing same are effectively-lost, a related object is to provide an acetylene hydrogenation catalyst which is relatively inactive in promoting hydrogenation' of olefins even in mixtures i containing a: major proportion-of olefins Although gas mixtures containing ethylene and other olefinsv derived bycthermal cracking of' alkanes. usually are:substantially. sulfur free, it is desirablein many'refinery operations -.to-.add others'refinery gases. which contain olefins to such gas mixtures when producing. ethylene. Such other refinery gases usually contain sulfur compounds, and, since such other gases are added in varyingamountsfrom time to time, the sulfur content of the resulting olefin containing mixture may vary from substantially zero to a considerable amount. Moreover, the sulfur is frequently encountered'in the form of compounds such as carbonyl sulfide (COS)' which'are quite difiicult to remove by conventionalmethods such as amine solution scrubbing.

Accordingly, another important object of this invention is to provide a selective hydrogenation catalyst which is both active and selective' for hydrogenating impurities in gas streams containing various=amounts of sulfur com- By. wayof example, gas-mixtures consist-- 2 pounds :andwbich willalso promote the hydrogenation of sulfur'compounds such ascarbonyl sulfide to yield-compounds which maybe more readily; removed.-

We: haveidiscovered'that a-;superior selective catalyst maybe readily formed by incorporating cobalt-molybdenauponi a carrier comprising hydraulic cement, ball clay: and alumina which may be rcducedto:activatethe cobalt molybdenae We have-further discovered that if the catalyst isto be both selectiveandsuflicientlyactive to completely'hydrog'enate: the acetylenic compounds at a=commerciallyfeasible rate, that the relative amount of the cobalt-molybdena must be maintained within aparti'cular range. Moreover, the: particular. carrier. material which we utilize has been found to be especially: suitable in that' it'will'iwithstand the rigorous regenerative procedure -to which the catalyst'must be subjected every; few weeks in order 'to remove polymer deposits. without: loss of mechanical I strength or impairment .of: catalyst activity or selectivity;

The catalytically. active material of 1' our. improved catalyst preferably is-a formiof cobalt-:molybdena complex having a mol ratio ofcobalt tovmolybdenum of-approximately ltol. UponreductionX-ray diffraction studies have indicatedthat thisreduced material had: a spinel 1 crystahform; i.e., the crystal form isclose packed cubic orface=centered cubic with oxygenlatornsatthe cornices and face centers and metal atoms in theinterstices. The exact'compositionof the reduced material is not known, but the -X-ray patterns'icould be explained by the formula Co MoO onpossibly an inverse? spinel,1namely,' MogC'oOr; beingpresent. Thelattice constant-is approximatelys8l46 angstroms and comparison of this value with other'crystals ofiknown composition and -formula induced :the: belief that. the: M004. was present: Combinations of. this materialland precipitated or. impregnated oxides oftcobalt or molybdenum are also suitable. Alternatively, intimate mixtures of cobalt and molybdenum oxides, such as are formed by, coprecipitation or impregnation upon a carrier and calcination, having other mol ratios than 1 to 1 may be employed with satisfactory results.

The ratioof cobalt to molybdenum in the catalyst is not particularly critical'and, although thel to'l ratio is preferred, ratios varyingbetween about-3 ml and-about 1' to 3-maybeemployedto advantageparticularly when therelativepercentage of' active material in the catalyst is high. In this instance it is believedthat the excessof either oxide substantially above the 1 to, 1 ratio' serves primarily as a promoter orcarrier-contributing to a minor extent to the'catalytic activity;

The relative amount of active material in thegcarrier may of course also-be'varied'over a range, andin'certain instances it has proved necessary to do' so in-order' to achieve the desired selectivity and activity for the gas stream with which the catalyst is utilized. In general, however, .the weight percentage of the catalytically active material .tototal catalyst .mass should be within the range of.about.2.5. to.about.l5 The most'suitable-amount of .activematerialwithin .this range depends upon several factors, .such. as, thecobaltto molybdenum ratio, the composition of the carrier, the composition of the gas stream to be treated, the'degree of acetylene removal required, and the concomitants of temperature, pressure andspace velocity.

The composition of the carrier material is'very important because it has-a marked-effect upon the activity of the catalytically active material and because of the extremely rigorous treatment to which catalysts of this type are subjected'in'service. Aftera-be'd of such catalyst has been in use two or three weeks, polymcrdeposits are formeduponthe surface which render the'catalyst inefi'ective'for-the removal of acetyl'enes. These deposits maybe burned oif the catalyst by passing steam and air 3 through the bed at a temperature of about 750 F., and within the bed the temperature may rise as high as 1200" F. due to the heat generated by oxidation of the polymer. This regenerative treatment usually involves a two or three day period, and considerable thermal shock'to the catalyst occurs. Following the treatment the catalyst which has become oxidized must be reduced with hydrogen at a high temperature, and following suchrreduction the temperature is again lowered to the operating range of about 400 to 500 F. Few carrier materials will withstand such regeneration treatment without undergoing physical or chemical breakdown greatly shortening the catalyst life. Such regenerative treatment must ,be repeated every two or three weeks during the life of the catalyst and, if a catalyst is to be suitable for economical commercial use, it must have an efiective life of fromv one to three years.

The carrier material of the catalyst of'this invention is a' mixture of clay and hydraulic cement with or without alumina. Various bonding clays such as kaolin, ball clay and certain refractory clays may be used, and various hydraulic cements such as Portland type cements and aluminous cements are satisfactory. The relative proportions of the ingredients in the carrier may be varied to some extent and still produce a quite satisfactory catalyst. For example, the amount of cement may vary from about 20% to about 85% of the weight of the carrier and the amount of clay may be varied from about 10% to about 50% of the weight of the carrier, while the amount of alumina in the carrier may vary from about to about 40% and, if desired, other materials such as magnesite or talc may be added as substitutes for, or in addition to, the alumina. Tests have shown that the alumina may be either high or low grade material.

Certain of the following specific examples further illustrate the improved catalyst of our invention and the manner in which it may be produced and utilized.

Example I A catalyst consisting of 4.4% cobalt-molybdena oxide complex supportedon a cement, clay, alumina carrier was prepared in the following manner: A solution of ammonium paramolybdate and cobalt sulphate having equal molar proportions of cobalt and molybdenum was neutralized with sodium hydroxide as a precipitating agent. Precipitation was accomplished by adding suificient sodium hydroxide to bring the pH within the range of 6.5 to 6.9. The resulting precipitate was washed, filtered and dried prior to incorporation in the carrier. X-ray difiraction studies of the precipitated, dried and reduced material indicated that it had the spinel crystal structure described above. The lattice constant was approximately 8.46 angstroms.

The dried filtrate was incorporated in the carrier by intimately mixing the following:

Parts by weight 5 A small amount of water was added during mixing to form a semi-plastic mass which was allowed to stand until it became partially dry. The partially dried material was then pelleted with the addition of 3% graphite as a lubricant into one-quarter inch diameter pellets with a Stokes pelleting machine. The pellets were then allowed to cure. A charge of this catalyst was placed in an isothermic reactor and was reduced for eight hours by passage of hydrogen gas at a temperature of about 850 F. through the charge. The temperature of the charge was then reduced to about 450 F. and a gas of the following composition was passed throughrthe catalyst bed lowing acetylenes content were obtained upon analysis of the efiluent:

4 after having been passed through water at such temperature as to add 3.5% water vapor to the gas mixture.

The pressure of the gas within the catalyst bed was p.s.i.g. and the space velocity through the bed was 600 computed on a dry gas basis at 60 F. and 14.7 p.s.i.g. (Space velocity as used herein means: volumes of dry gas passing the catalyst bed per hour divided by the volume of the catalyst bed.) This test was conducted for 51 hours and the temperature of the gas in the catalyst bed varied from about 450 to about 500 F. The results i of this test are tabulated below:

Average Bed temacetylenes Hours on stream perature in in efliuent degrees F. in parts per million Thus it will be seen that the acetylenes in the gas stream were virtually completely eliminated and that accordingly the catalyst is sufl'iciently active for the acetylene removal reaction. The efiluent gas was analyzed from time to time for olefins and it was found that the average amount of olefins hydrogenated was less than 1.0% of the total olefins present. Accordingly, the catalyst is quite selective.

Example II A catalyst similar to that of the foregoing example,

except that an all alumina carrier was employed, was tested under identical conditions. This catalyst contained about 4.4% of the cobalt-molybdena prepared by precipitation in the same manner as described in Example I. Catalyst pellets were formed by admixing the following materials:

Parts by weight The pellets were cured in air and were charged into an isothermal reactor and reduced with hydrogen as in Example I.

A gas having an identical composition as the gas in Example I was passed through the catalyst bed and the fol- Bed tem- Acetylenes perature in in eflluent Hours on stream degrees F. in parts per million The space velocity during this test was 600'as in the pre- ViQ lK iP P .By comparing, the amount of acetylenes in the eflluent it-will beseen that this catalyst is not nearly so active as the catalyst of Example I, the average acetylenes content of the effluent being approximately-five times as great. Accordingly, the alumina carrier catalystdoes not appear to be as effective as the catalyst having, a cement and clay carrier.

Example III A- catalyst similar to that of Example I, but containing; 20% cobalt-molybdena instead of- 4.4% supported on a carrier of cement, clay and alumina, was chargedin an isothermic reactor and reduced'as in Example I. A gas-of the following composition admixed-with 5.6% steam was passed through the catalyst-bed.

Constituent: Mol'percent Butene 0.2 Butadiene 0.3 Acetylene 0.4 Propylene 1.2 Ethylene 33" Carbon monoxide 1.0 Hydrogen 29.4 Methane 34.5

This gas was conducted through the bed at'a space velocity'of 1000. The temperature of the bed was maintained between 220 and 450 F. The results-of this test were as follows:

Percent olefins Acetylene effluent in parts per million Days on stream Example IV A catalyst was prepared similar to the catalyst of Example I but containing approximately cobalt-molybdena prepared by the method set forth in Example I. This catalyst was charged into an isothermal reactor and reduced as in Example I. A gas of the following composition was passed through-the reactor at a space velocity of about 1000 and at a temperature varying between 450 and 500 F.

Constituent: Mol percent Butene 0.2 Butadiene 0.5 Acetylene 0.2 Propylene -6.0 Ethylene 20.3 Carbon monoxide 1.2 Hydrogen 21.0 Methane 44.1

The pressure was 200 p.s.i.g. The gas was passed through the catalyst bed for a period of eight days during which time it was found to effectively remove virtually all of the acetylene without undesirable hydrogenation of olefins.

At the end of the eighthday'approximately.onelgraimof carbonyl sulfide (COS)' was adddL-for. each. 100. cubic feet of gas measured under standard conditions. Analysis of the outlet gas was made at various times from the eighth'through the sixteenth dayof-the-test and it was found that the average acetylene content of the effiuent was somewhat less than 20 parts per million. Such analysis also indicated that none of the olefins were hydrogenated. From this example itis apparent thata catalyst containing -10% cobalt-molybdenacomplex on the cement, clay, alumina carrier is entirely satisfactory for use in purifyingg'as-streamswhieh'are sulphur-free or which contain small amounts of sulphur compounds. Moreover, this catalyst maintained very good activity and selectivity with both gas-streams.

Example V complex wouldbes'ufliciently selectiveforuse with gas streams containing relatively large amounts of'sulphur.

The results of "this test'utilizing the sulphurcontaining' gas stream were as follows:

,: Average Bad temacetylene Dawson-stream" peraturei'n' ineflluenv hiydto-- degrees F. in parts genated per million 7 From these data it will be apparent that'the20%' active material catalyst is much too active to be selective even with gas streams containing'large sulphur'concentrations. Moreover, in order: to determine whether'the catalyst could be. rendered. effective by steaming, the'bed' was To determine whether. the catalystof Example .I, which consisted of 414%v cobalt-molybdena on the cement, clay and. alumina. carrier,-.was suitable for. use in removing acetylene from gas -streamscontaining sulphur,v the following gasstream'was passed through abed'ofthe reduced catalyst-of'Example I;

Component: Mo percent Acetylene 0.4 Butene I 0.2 Butadiene 0.5 Propylene 1L2 Ethylene 33.0 Carbon monoxide 1.4 Hydrogen 29.0 Methane 33.9

Carbonyl sulfide in an amount of two grains per hundred standard cubic feet of gas was added to the stream giving a sulphur content of about 16 p.p.m. The gas also contained about 5.5% water vapor.

The catalyst bed was activated by reduction as in Example I and the gas was conducted through the bed at a space velocity of 1000, a pressure of p.s.i.g. and a temperature varying from 450' F. to 600 F. The results of this test were as follows:

Analysis of the efliuent gas stream indicated that only 0.6 mol percent of the olefins were hydrogenated. Moreover, the cobalt-molybdena catalyst has been found to be effective in hydrogenating the carbonyl sulfide to compounds which are much more readily removable by conventional means. Thus this catalyst is also an eifective desulfurization catalyst.

It will be noted from the above table that the average acetylene leakage was somewhat higher than that reported in Example I.' This is due to the inhibiting efiect of the sulphur upon the catalyst. At a temperature of about 600 F., however, the activity of the catalyst was sulficiently high to effectively remove all but ten to fifteen parts per million of the acetylenepresent.

Example VII A catalyst containing about 14% by weight cobaltmolybdena and having a molar ratio of cobalt to molybdena or" about 1 to 1.6 was prepared from the following ingredients;

The cobalt nitrate was diluted, with tap water to such extent that the concentration of cobalt measured as cobalt oxide therein was 15%. This solution was admixed with the alumina and mulled for five minutes. The mo1ybdenum trioxide was dissolved in approximately 15 parts by. weight of 29% ammonia solution, and theresulting ammonium molybdate solution was added to the aluminacobalt-nitrate mixture, and the whole admixture was mulled for five minutes more. The resulting pasty mass was then calcined in air for eight hours at 900 F. The calcined product was then cooled and mulled with the Portland cement and the clay. During this mulling stage sufiicient water was added to produce a moist formable mass which was allowed to stand until it became partially dry. The partially dried mass was then pelleted with the addition of graphite as described in Example I. Catalyst produced as described above may be utilized to remove undesired impurities by catalytic reaction on gas streams containing organic sulphur compounds.

From the foregoing examples it will be readily apparent to those skilled in the art that a superior catalyst has been provided which is particularly well suited for the selective hydrogenation of acetylenes in gas streams containing olefins which it is not desired to hydrogenate. Moreover, the catalyst of this invention is quite suitable for gas streams which contain relatively large amounts of sulphur compounds which ordinarily act as catalyst poisons in such reactions.

Various changes and modifications in catalyst of this invention, such as will present themselves to those familiar with the art, may be made without departing from the spirit of this invention.

What is claimed is: a

1. A shaped hydrogenation catalyst suitable for the selective hydrogenation of acetylene in the presence of olefins, said catalyst comprising finely divided cobaltmolybdena supported upon a carrier formed into catalyst shapes, the cobalt-molybdena being present in an amount between about 2.5 percent and about 15 percent by weight of the catalyst and the molal ratio of cobalt to molybdena being between about 1 to 3 and about 3 to 1, and the carrier comprising set hydraulic cement and bonding clay, the amount of cement being between about 20 percent and about percent and the amount of clay being between about 10 percent and about 50 percent by weight of the carrier.

2. The catalyst of claim 1, the ratio of cobalt to a spinel type crystal structure characterized by a lattice spacing of about 8.46 angstrom units determined by X- ray difiraction.

5. A shaped catalyst suitable for hydrogenation, said catalyst comprising finely divided cobalt-molybdena supported upon a carrier formed into catalyst shapes, the cobalt-molybdena being present in an amount between about 2.5% and about 15% by weight of the catalyst and the molal ratio of cobalt to molybdena being between about 1 to 3 and about 3 to 1, and the carrier comprising set hydraulic cement and bonding clay, the amount of cement being between about 20 percent and about 85 percent and the amount of clay being between about 10 percent and about 50 percent by weight of the carrier and said carrier also including alumina.

6. The catalyst of claim 5, the ratio of cobalt to molybdena being about 1 to 1.6 and thetotal cobaltmolybdena being about 14 percent by Weight of the catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 2,625,519 Hartig Jan. 13, 1953 2,665,259 Bufiett Jan. 5, 1954 2,687,381 Hendricks Aug. 24, 1954 OTHER REFERENCES Catalysis by S. Berkman et al., Reinhold Publishing Co., N.Y., 1940, pages 473-477. 

1. A SHAPED HYDROGENATION CATALYST SUITABLE FOR THE SELECTIVE HYDROGENATION OF ACETYLENE IN THE PRESENCE OF OLEFINS, SAID CATALYST COMPRISING FINELY DIVIDED COBALTMOLYBDENA SUPPORTED UPON A CARRIER FORMED INTO CATALYST SHAPES, THE COBALTL-MOLYBDENA BEING PRESENT IN AN AMOUNT BETWEEN ABOUT 2.5 PERCENT AND ABOUT 15 PERCENT BY WEIGHT OF THE CATALYST AND THE MOLAL RATIO OF COBALT TO MOLYBDENA BEING BETWEEN ABOUT 1 TO 3 AND ABOUT 3 TO 1, AND THE CARRIER COMPRISING SET HYDRAULIC CEMENT AND BONDING CLAY, THE AMOUNT OF CEMENT BEING BETWEEN ABOUT 20 PERCENT AND ABOUT 85 PERCENT AND THE AMOUNT OF CLAY BEING BETWEEN ABOUT 10 PERCENT AND ABOUT 50 PERCENT BY WEIGHT OF THE CARRIER. 